Multi-scale structuring of the oil-water interface in fat crystal-stabilized emulsions

脂肪结晶对食品油包水（W/O）乳剂（如黄油、人造黄油、冰淇淋和低脂巧克力）的形成和质量属性有显著影响，在这些乳剂中，水以细小液滴的形式分散在连续的油/脂肪网络中。在这些产品中，皮克林三酰基甘油（TG）晶体包裹住分散的水滴，有助于产品的质地和长期稳定性，防止液滴聚结和目视相分离。卢梭实验室最近的两项发现为在分子和微观结构长度尺度上系统地构建脂肪晶体稳定的W/O乳剂的物理特性铺平了道路。我们最近已经证明，通过使用与tg分子结构相容的界面吸附液态表面活性剂，可以“强迫”表面无活性的脂肪晶体直接在分散的水滴表面结晶。其次，在密闭环境下对脂肪晶体稳定的水乳状液进行剪切冷却，导致脂肪晶体聚集成球状、茧状的微观结构。我们的研究导致了一种新形式的Pickering-type稳定化的发展，其中分散的水滴被封装在厚的晶体壳中。目前还处于起步阶段，对这些现象的机械理解是充分理解和利用这些结构乳剂的必要条件。许多研究工具，包括拉曼光谱，流变学和显微镜将被使用。我的小组还提出使用同步加速器x射线衍射来原位确定乳化液油水界面上tg和表面活性剂的真实取向。总之，这些技术将允许在分子和微观结构长度尺度上专门设计和构建具有创新结构的pickering稳定W/O乳液。获得的基本理解将导致更好的乳液稳定性，从而增加食品和其他应用的保质期。此外，随着W/O食品乳剂越来越被食品加工商视为减少卡路里的工具，这项高度可行的研究将成为开发更健康加工食品的新工具。

Fat crystallization has a pronounced influence on the formation and quality attributes of food water-in-oil (W/O) emulsions such as butter, margarine, ice cream and low-fat chocolate, where water is dispersed as fine droplets within a continuous oil/fat network. In such products, 'Pickering' triacylglycerol (TG) crystals englobe dispersed water droplets and contribute to product texture and long-term stability against droplet coalescence and visual phase separation. Two recent discoveries in the Rousseau laboratory are paving the way to the systematic structuring of the physical properties of fat crystal-stabilized W/O emulsions at the molecular and microstructural length scales. We have recently shown that it is possible to 'coerce' otherwise surface-inactive fat crystals into crystallizing directly at the surface of dispersed water droplets by using interfacially-adsorbed liquid-state surfactants with a molecular structure compatible with the TGs. Secondly, shear-cooling of fat crystal-stabilized W/O emulsions within a confined environment induces fat crystal agglomeration into spheroidal, cocoon-like microstructures. Our research has led to development of a new form of Pickering-type stabilization where dispersed aqueous droplets are encapsulated within thick crystal shells. Currently in its infancy, a mechanistic understanding of these phenomena is necessary to fully understand and exploit these structured emulsions. Numerous research tools including Raman spectroscopy, rheology and microscopy will be used. My group also proposes the use of synchrotron X-ray diffraction to establish in-situ the true orientation of TGs and surfactants at the emulsion oil-water interface. Together these techniques will permit the dedicated design and construction of innovative structured Pickering-stabilized W/O emulsions at the molecular and microstructural length scales. The fundamental understanding gained will result in better emulsion stability and therefore increased shelf life for foods and other applications. As well, as W/O food emulsions are increasingly seen as vehicles for calorie reduction by food processors, this highly-feasible research will be a novel tool for the development of healthier processed foods.